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Astigmatism Correction

The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

J T L Thong – 1st expert on this subject based on the ideXlab platform

  • a robust focusing and Astigmatism Correction method for the scanning electron microscope
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    This paper discusses a new approach to focusing and Astigmatism Correction based on the fast fourier transforms (FFTs) of scanning electron microscopy (SEM) images. From the FFTs, it is possible to obtain information on the severity of the defocus and Astigmatism. This information is then processed by an algorithm to perform real-time focusing and Astigmatism Correction on the SEM. The algorithm has been tested on defocused and astigmatic images of different samples, including those with highly directional features. Experiments show that the images obtained after running the algorithm can be as good as those that an experienced SEM operator can achieve.

  • a robust focusing and Astigmatism Correction method for the scanning electron microscope part iii an improved technique
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.

  • A robust focusing and Astigmatism Correction method for the scanning electron microscope—Part III: An improved technique
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.

J C H Phang – 2nd expert on this subject based on the ideXlab platform

  • a robust focusing and Astigmatism Correction method for the scanning electron microscope
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    This paper discusses a new approach to focusing and Astigmatism Correction based on the fast fourier transforms (FFTs) of scanning electron microscopy (SEM) images. From the FFTs, it is possible to obtain information on the severity of the defocus and Astigmatism. This information is then processed by an algorithm to perform real-time focusing and Astigmatism Correction on the SEM. The algorithm has been tested on defocused and astigmatic images of different samples, including those with highly directional features. Experiments show that the images obtained after running the algorithm can be as good as those that an experienced SEM operator can achieve.

  • a robust focusing and Astigmatism Correction method for the scanning electron microscope part iii an improved technique
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.

  • A robust focusing and Astigmatism Correction method for the scanning electron microscope—Part III: An improved technique
    Scanning, 2006
    Co-Authors: J C H Phang, J T L Thong

    Abstract:

    As described in a previous work, a new technique has been developed to perform automatic focusing and Astigmatism Correction on any general scanning electron microscope (SEM) sample ranging from gold-on-carbon to integrated circuit (IC) tracks. In this work, various improvements made to this technique are reported. They include the implementation of direct control of the SEM and the development of three new algorithms, namely the adaptive fast Fourier transform (FFT) algorithm, the coarse focusing algorithm, and the fine focusing algorithm. Direct control reduces the communication time with the SEM while the three new algorithms are integrated with the existing technique to make it even more robust to noise and to extend it to correct images with any degree of defocus and Astigmatism. The enhanced focusing and Astigmatism Correction algorithm is able to perform the Correction in a shorter time while maintaining the accuracy of the original algorithm even under noisy conditions.

Javier Mendicute – 3rd expert on this subject based on the ideXlab platform

  • vector analysis of Astigmatism Correction after toric intraocular lens implantation
    Journal of Cataract and Refractive Surgery, 2015
    Co-Authors: Eva Maria Krall, Javier Mendicute, E M Arlt, Melchior Hohensinn, Sarah Moussa, Gerlinde Jell, Jorge L Alio, Ana B Plazapuche, Lucia Bascaran, Gunther Grabner

    Abstract:

    Purpose To determine astigmatic changes by vector analysis and postoperative refractive and visual outcomes after implantation of the monofocal aspheric bitoric AT Torbi 709M toric intraocular lens (IOL). Setting Three centers in Salzburg, Austria, and Alicante and San Sebastian, Spain. Design Prospective interventional case series. Methods Preoperative and postoperative visual acuity, subjective and objective refractions, and corneal radii using a topographer were examined in all patients. All patients had postoperative examinations within the first week and at 6 to 12 weeks. Astigmatic changes were evaluated using the Alpins vector method based on 3 fundamental vectors as follows: target induced Astigmatism (TIA), surgically induced Astigmatism (SIA), and difference vector. The various relationships between these 3 vectors were calculated, providing an extensive description of the astigmatic Correction achieved. Results Eighty-eight eyes (71 patients) were included. Postoperatively, refractive cylinder was reduced significantly ( P Conclusion Implantation of the toric IOL was safe and effective for the treatment of eyes with cataract in combination with preexisting regular corneal Astigmatism over a short-term follow-up. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

  • foldable toric intraocular lens for Astigmatism Correction in cataract patients
    Journal of Cataract and Refractive Surgery, 2008
    Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert Montesmico

    Abstract:

    Purpose To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. Setting Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. Methods This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. Results The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from −2.34 D ± 1.28 (SD) to −0.72 ± 0.43 D (P Conclusions The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.

  • foldable toric intraocular lens for Astigmatism Correction in cataract patients
    Journal of Cataract and Refractive Surgery, 2008
    Co-Authors: Javier Mendicute, Cristina Irigoyen, Jaime Aramberri, Ana Ondarra, Robert Montesmico

    Abstract:

    PURPOSE: To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting Astigmatism in patients having cataract surgery. SETTING: Ophthalmology Service, Donostia Hospital, San Sebastian, Spain. METHODS: This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal Astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. RESULTS: The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from 2.34 D G 1.28 (SD) to 0.72 G 0.43 D (P<.01). Vector analysis of attempted versus achieved Correction showed that 100% of eyes were within G1.00 D and 80% and 93.9% were within G0.50 D for J0 and J45, respectively. The mean toric IOL axis rotation was 3.63 G 3.11 degrees, with rotation less than 10 degrees in 96.7% of eyes. CONCLUSIONS: The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting Astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.